Certain pre-existing conversion algorithms used in converting a colour image into a grayscale image involve creating the grayscale image by reference to only the luminance values of pixels within the colour image.
However, in many instances, the colour image will contain isoluminant regions such that visual contrasts which are readily visible in the colour image may not be readily visible or distinguishable in the resulting grayscale image.
Other pre-existing algorithms tend to employ multidimensional scaling to covert a colour image to a grayscale image. However, such processes tend to involve the processing of relatively large numbers of variables which is time and resource intensive and therefore unsuitable for use real-time applications such as printing.
Examples of such pre-existing colour image conversion algorithms are described in the following cited publications:                (i) Contrast Maximizing and Brightness Preserving Colour to Grayscale Image Conversion, CGIV 2008, IS&T's Fourth European Conference on Colour in Graphics, Imaging and Vision 10th International Symposium on Multispectral Colour Science, Jun. 9-13 2008, Terrassa-Barcelona, Esparia, by M Qiu, G. Finlayson and G. Qiu. (hereafter referred to as the “C2GB0-1” algorithm); and        (ii) The Decolorize Algorithm for Contrast Enhancing, Color to Grayscale Conversion, Pattern Recognition, V40 (2007), pp. 2891-2896). By M. Grundland and N. Dodgson (hereafter referred to as the “Decolorize” algorithm).        